Technical Abstract:
Fescue toxicosis in cattle, caused by ingestion of endophyte-infected fescue (EIF), is associated with decreased feed intake, growth, milk production and reproductive efficiency as well as decreased resistance to heat, transportation and immune stress. Increased inflammatory response to immune challenge was also reported in steers grazing EIF. The purpose of this study was to evaluate whether in utero exposure to ergot alkaloids from EIF seed fed to cows during the dry period would affect the developmental pattern of plasma indicators of birth stress in newborn calves. Starting at 90-d prepartum, multiparous Holstein cows were fed endophyte-free fescue seed (CON; n = 9) or EIF seed as 10% of the as-fed diet (INF; n = 8). Newborn calves were separated from their dams after birth. Blood samples were collected from calves within 12 h of birth (d 0) and then at d 4, 7, 14, 21, 28, 35, and 42. No differences (P > 0.05) were found between CON and INF calves on d 0 in BW (41 ± 1 kg) and in plasma concentrations of urea nitrogen (PUN; 7.1 ± 0.4 mg/dL) and the acute phase protein, Hp (0.20 ± 0.04 mg/mL). However, on d 0, plasma concentrations of nitrate+nitrite (NOx; an estimate of NO production and neonatal vascular adaptation) were lower (155 vs. 223 µmol/L; P < 0.01), whereas XO activities (generation of oxygen-derived free radicals) were greater (9.07 vs. 3.27 mU/mL; P < 0.01) in INF than in CON calves. Plasma Hp concentrations were greater (P < 0.05) at d 4 (0.44 vs. 0.29 mg/mL) and 7 (0.55 vs. 0.38 mg/mL) in INF than in CON calves although no differences were found thereafter. Between d 4 and 42, time related developmental changes in calf plasma PUN, NOx and XO levels were observed (P < 0.01) but they were not affected by the dam’s dietary treatment. These results suggest that feeding toxin-associated components of EIF seed to dairy cows altered selected plasma indicators of birth stress in newborn calves during the first week of life but had no long-term effect on the developmental pattern of these mediators.